In the highly mechanized modern world, more and more work is done by mechanical equipment, which humans cannot do without. With the help of machinery, we can efficiently complete work. With them, our lives are also more convenient, and the rapid development of society is also thanks to them.
In order to adapt to the development of society and improve work efficiency, mechanical equipment is becoming larger and more efficient. These large machinery can efficiently complete their work without their core component, hydraulic cylinders. Many gravity machinery must use hydraulic cylinders as the power transmission core, and only with the help of hydraulic cylinders can these tasks be completed.
Hydraulic cylinder is a hydraulic equipment that converts hydraulic energy into mechanical energy and performs linear reciprocating or oscillating motion. Its structure is relatively simple, and when performing reciprocating motion, it moves smoothly. It is widely used in various engineering machinery, ships, machine tools, and even national defense equipment industries.
The principle of hydrostatic transmission proposed by Pascal in the 17th century laid the foundation for the later development of hydraulic cylinders.
In 1795, the British used water as a medium and applied it in industry in the form of a hydraulic press, giving birth to the world's first hydraulic press.
In 1905, the working medium was changed from water to oil, and the performance was further improved.
After World War I, mankind entered the industrial era, and hydraulic transmission began to be widely used.
There are two types of piston type hydraulic cylinders: single piston cylinder and double piston cylinder. Single piston hydraulic cylinders only have a piston rod at one end, with oil outlet and return ports at both ends to achieve bidirectional movement. They are also known as double acting cylinders and are commonly used in construction machinery such as hydraulic excavators.
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The dual piston hydraulic cylinder has piston rods extending at both ends, and its composition is basically the same as that of a single piston rod hydraulic cylinder. When oil enters the right chamber of the hydraulic cylinder and returns to the left chamber, the piston moves to the left, and vice versa.
Due to the same diameter of the piston rods on both sides, the effective area of action on both ends of the piston is the same. If oil with the same pressure and flow rate is input to the left and right ends, the thrust and reciprocating speed generated by the piston are also equal. This type of hydraulic cylinder is commonly used in places with the same round-trip speed but little thrust, such as grinding machine workbenches.
So, do you still have the question of where the power of this hydraulic oil comes from and where the oil has gone back? Perhaps you can understand this picture below.
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Plunger type hydraulic cylinder is a single acting hydraulic cylinder that can only achieve movement in one direction based on hydraulic pressure. The return stroke of the plunger depends on other external forces or the weight of the plunger. The plunger does not contact the cylinder body, and the end of the plunger type is under pressure. To ensure sufficient thrust and stability of the plunger, the plunger is generally thick and heavy, and horizontal installation can easily cause unilateral wear. It is suitable for vertical installation and is used on long-distance machine tools.
There are two one-way valves on a plunger cylinder, with opposite directions. When the plunger moves in one direction, negative pressure is generated in the cylinder. This is when one one-way valve opens and the liquid is sucked into the cylinder. When the plunger moves in the other direction, the liquid is compressed and the other one-way valve is opened, and the liquid sucked into the cylinder is discharged. This working method forms continuous oil supply after continuous movement.
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A swing hydraulic cylinder is an actuator that outputs torque and achieves reciprocating motion, also known as a swing hydraulic motor. It has two forms: single blade and double blade. The stator is fixed on the cylinder body, and the blades and rotor are connected together. The blades will drive the rotor to swing back and forth according to the oil inlet direction, and are used in high torque fields, engineering machinery, and vehicles.
When one oil port receives pressure oil and the other oil port returns oil, the blades swing in one direction under pressure, driving the shaft to deflect at a certain angle. When the inlet and outlet ports exchange, the motor reverses.
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Its manufacturing starts from this cylinder, first cutting the steel pipe into the required length and threading it on the inner walls of both ends.
Cut the steel column into the required dimensions, and machine the solid steel column into a piston rod. This piston rod is hydraulically driven to transmit power to the machine, and threads and cylindrical shapes of various diameters are carved at one end. This can have a cushioning effect when the hydraulic cylinder drives the machine to run, and the other end of the piston rod is installed on the piston.
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Take a section of steel column and make it into a piston. Use a drill bit to make a hole in the center of one end of the piston, and make a groove in the outer ring to make the piston. Install sealing rings in both the inner and outer grooves.
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Install the piston with the sealing ring on one end of the piston rod and tighten it with a nut.
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The automatic welding machine welds the cover and oil inlet and outlet at one end of the cylinder barrel, inserts the piston rod into the hydraulic cylinder, and tightens the liquid cylinder and piston rod against the thread.
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After the hydraulic cylinder is installed, hydraulic oil is injected into the oil inlet, and the hydraulic rod will automatically extend. Observe whether there is any oil leakage from the hydraulic rod.
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Spray paint on the surface of the hydraulic cylinder to prevent rust, and after manufacturing, it is used on various mechanical equipment to exert its strong power.
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After a period of use, hydraulic cylinders may experience oil leakage due to piston rod strain, aging of sealing rings, and other reasons. Oil leakage can affect work efficiency and even lead to mechanical failures. Therefore, how to ensure that hydraulic cylinders do not leak oil requires good sealing performance and the ability to withstand high pressure. Hydraulic cylinder parts require high precision in welding and machining, and various structural sealing rings are also used.
Oil leakage is allowed within a controllable range. The piston rod is in a dry friction state during reciprocating motion, which will exacerbate the wear of the parts and reduce the service life. Therefore, a certain amount of oil leakage is allowed to play a role in lubrication and reducing friction. However, it is required that the piston rod cannot leak oil when it is stationary, and there are strict requirements for the amount of oil leakage. If it exceeds the limit, it is considered oil leakage.
Why can the oil delivery pipe connecting the hydraulic cylinder withstand such high pressure when it is so thin?
I believe many friends have this question. Hydraulic oil pipes are composed of multiple layers of pressure resistant rubber, with a reinforced layer woven with steel wire in the middle. The number of woven layers is increased according to different pressure levels to ensure their pressure resistance level.
The most important point is what kind of equipment, how much pressure is required, and the hydraulic oil pipes have corresponding pressure resistance levels, which are strictly calculated before production.
Hydraulic oil pipes have two processes: winding and weaving, and the corresponding pressure is also different
The standard for steel wire braided hydraulic hoses is GB/T 3683-2011
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The standard for wire wound hydraulic hoses is GB/T 10544-2003
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From two standards, the pressure borne by steel wire winding is significantly greater than that of steel wire weaving. Generally speaking, the price of steel wire winding hose is higher than that of steel wire weaving hose
The piston rod of a hydraulic cylinder will be exposed to the outside for a long time during operation, which is prone to corrosion, oxidation, or damage, causing damage to the piston rod and oil leakage. In order to protect the service life of the piston rod, a retractable protective sleeve will be installed on the piston rod.
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Hydraulic cylinders have a history of over a hundred years since their inception. China began producing hydraulic cylinders in the 1950s, with a relatively late start in the industry and low levels of technology and craftsmanship. They have basically achieved autonomy in the low-end market of hydraulic cylinders and have a large market share internationally. However, in the high-end hydraulic cylinder market, we still have a significant gap compared to the United States and Germany.
But with years of catching up with hydraulic cylinder companies in our country, we have successively produced the world's longest hydraulic cylinder, with 8000 hours of continuous operation and faultless hydraulic cylinder. We are gradually surpassing each other, and now China's engineering machinery is world-class, which cannot be separated from the contribution of hydraulic cylinders. We hope that China's hydraulic cylinders can also achieve the best in the world, safeguarding the development of China's manufacturing industry.